Most of the general aviation and commuter fleets of the world are fitted with ice protection systems. These systems usually include de-icer apparatus installed to cover various parts, including the wings, propellers and intake ports of the aircraft. The de-icer apparatus typically consist of one or more flexible members affixed to conform to the aerodynamic shape of the covered part of the aircraft. These de-icers are often pneumatic rubber boots having means by which the boots are sequenced through inflation and deflation cycles to crack and remove the ice that becomes attached thereto. Thus, the rubber composition of the boot is highly stressed and worn from continual pneumatic flexing as well as from being exposed to extreme temperatures and harsh environmental conditions.
More specifically, the function of these de-icing boots is to remove ice from the edge of the wing surface. This is accomplished by the de-icing boot cycling through an inflation and deflation process. As the rubber expands and then contracts, the ice breaks off and rids the plane of the excess weight of the ice. However, at low temperatures of at least about 5 degrees Fahrenheit, the ice removal efficiency of the de-icing boot is greatly reduced when compared to the efficiency of the ice removal at higher sub-freezing temperatures.
Consequently, there is a need for a special composition particularly adapted to be applied to flexible surfaces, such as rubber surfaces of de-icing boots, to act as a flexible protective agent and preservative and to restore and maintain flexibility of the rubber, thereby insuring long life. Such a composition must be able to withstand both the extreme environmental conditions to which aircraft are exposed and the high speeds of the aircraft.
In addition, de-icer apparatus is usually installed on the leading edges and front portions of various parts of aircraft so that they are highly visible. Thus, it is important that the boots maintain an attractive appearance despite the continual weathering and harsh conditions to which they are subjected. A composition for treating rubber surfaces is needed which will cosmetically enhance and improve the appearance of the surface as well as to act as a preservative and protectant.
Conventional preservative and protective compositions consisting of styrene acrylic and polyethylene emulsions are well known in the art. For example, U.S. Pat. No. 3,440,188 (Burdick et al) discloses a water base polish containing 70 to 80 percent by weight of an ethylene wax and an unspecified amount of a synthetic resinous polymer consisting of a homopolymer or copolymer styrene, and/or acrylic and methacrylic acid esters. The primary purpose of the composition disclosed in Burdick et al is to provide enhanced characteristics in all of the polish film properties, such as gloss, waterspot resistance, resistance to powdering or dusting, slip resistance, recoatability, removability, buffability, scuff resistance and the like. Another patent that discloses the use of styrenes in conjunction with suitable ethylene based waxes in U.S. Pat. No. 3,728,418 (Gleason). The composition in Gleason provides for a floor polish with a composition of a styrene copolymer emulsion and a styrene multi-polymer emulsion that inhibits the plasticizer in the vinyl floor covering from migrating from the vinyl floor covering into the floor polish.
Other prior art discloses de-icing or anti-icing compositions such as those disclosed in European applications Nos. 50,700 and 257,720 and U.S. Pat. Nos. 4,358,389 (Konig-Lumber et al), 4,636,324 (Murase et al), 4,744,913 (Salvador et al) and 4,954,279 (Ma et al). Most of these compositions contain a high percentage of glycol that reduces the freezing point of the water which melts the ice and thereby eliminating it from the surface to which it is applied. One patent (Murase et al) discloses a composition that contains a large percentage of organopolysiloxane which prevents the formation of ice on the surface to which it is applied. As is the case with the de-icing compositions containing glycol, the organopolysiloxane composition does not have any other protective characteristics and therefore, offers no advantage other than preventing the formation of ice.